This study is a collaboration between intramural and extramural investigators. As such, it expands the Polish component of an extramurally funded case-control study of breast cancer in Polish- American and Polish women. A study in Poland offers a unique opportunity for assessing the role of occupational risk factors, since a large proportion of females are employed in the workforce and have been for some time. In addition, the study offers the opportunity for assessing a number of unresolved risk factors for breast cancer, including the roles of body size, physical activity, alcohol consumption, cigarette smoking, and histories of induced abortion. These factors will be examined in relation to a number of metabolic genes to clarify risk relationships and to develop a better understanding of their underlying biologic mechanisms. This contract with investigators at the Maria Sklodowska-Curie Memorial Center and Institute of Oncology in Warsaw will allow accrual of study subjects in Warsaw (which was the focus of the extramural investigation) as well as in the heavily industrialized city of Lodz. Cases will be ascertained over a two and half year period, which will be a continuation of one year beyond that which was included in the original extramural funding. This will enable ascertainment of approximately 1,500 women with incident breast cancers in Poland and an equal number of population controls. Personal interviews will be conducted, mainly in the homes of study subjects, to ascertain information on standard breast cancer risk factors, as well as on a variety of postulated environmental and occupational factors. Subsequent to the completion of home interviews, subjects will be visited by a phlebotomist, who will collect blood and urine samples and obtain anthropometric measurements. In Warsaw, the study will also involve use of physical activity monitors and retrieval of vacuum cleaner bags of dust samples which can be used for assessment of environmental contaminants.